Pain

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Questions Received:

  1. I have a burning sensation in one area of my shoulder, frequently. It feels like a hot pan has been sat on the same spot, occuring often, in the same spot, but goes away after a few minutes.

  2. I want know detail description of "Physiological Pain - Gate Control Theory and Endogenous Analysis". If you can help me I will be very thankful to you.

  3. I have had a headache for 3 days and nights worse when I cough or sneeze or when I get up. Do you think I should see the doctor? My periods started 2 days ago.

  4. After cooking with hot chillies, my finger tips burned for a long period of time (and still are as I type this), presumably because of the chemical "Capsaicin," which I read about in one of your articles. How can I relieve this burning in my fingertips? I have washed my hands many times since I was cooking, and even tried soaking my fingertips in milk. But those didn't work. Any suggestions?

  5. Having smashed both left & right calcanii (heel bones), under gone surgery 3 times. Last operation sub-talar fusion. Constant pain. Tried DHC 120mg, Co-Codamol 30/500, Voltarol 75mg, Amitriptyline 50mg etc. GP wants me to try morphine but I have refused as I am only 31 years old. Please help.

Responses:

I have a burning sensation in one area of my shoulder, frequently. It feels like a hot pan has been sat on the same spot, occuring often, in the same spot, but goes away after a few minutes.

6th April 1999

There are several situations that can give rise to pain in the shoulder region, and the main ones are listed below. However, we are not in a position to provide diagnoses, and if you are still troubled by the sensation it is advisable to visit your doctor for investigation and possible treatment:

I want know detail description of "Physiological Pain - Gate Control Theory and Endogenous Analysis". If you can help me I will be very thankful to you.

13th March 2000

In 1965 Melzack and Wall proposed a gating mechanism within the substantia gelatinosa of the spinal cord, a specialised area through which sensory information has to pass before being relayed to the sensory cortex. A considerable proportion of the sensory information reaching the spinal cord is filtered out, and only a small proportion is sent onwards to the higher centres of the brain for further processing. Sensory fibres of all modalities (eg: pain, temperature, touch, pressure, vibration) enter the posterior grey matter of the spinal cord and connect with a variety of neurons, including a column of small neurons in the substantia gelatinosa. The pattern and quantity of impulses reaching the substantia gelatinosa determine the way in which impulses will be filtered before onward transmission to the brain.

This can be best understood by thinking of the effects that excitatory and inhibitory neurotransmitter chemicals have on neurons of the gate control mechanism. Opening of the gate is achieved by the release of excitatory neurotransmitter molecules at synapses and closure is brought about by inhibitory neurotransmitter molecules. Impulses carried by fast-transmitting sensory neurons from mechanoreceptors in the skin have the effect of closing the gate. This prevents impulses arising from pain receptors (nociceptors) and arriving via slow-transmitting neurons being relayed to the cortex. If a part of the body is injured - eg: banging the elbow or knee against a table edge - several seconds elapse before the full pain intensity is experienced. This is because the peripheral pain fibres conduct impulses at a relatively slow rate. If the injured area is rubbed vigorously imediately after the painful stimulus occurs, the degree of pain perceived is significantly reduced. This is because stimulation of the mechanoreceptors with fast conducting fibres has the effect of closing the gate at the spinal cord level. This is the rationale behind using trans electronic nerve stimulation (tens) as a means for relieving pain, particularly chronic pain.

The higher centres of the brain also influence the gate control mechanism. Endogenous opiates (enkephalins, endorphins and dynorphins) are the body's own natural 'pain killers', and when they are released they have the effect of inhibiting the release of substance P, an excitatory neurotransmitter. Some of the techniques used by nurses to reduce stress and anxiety in patients will, in theory, promote the release of endogenous opiates thereby reducing the amount of pain that a person might otherwise experience.

Notes About Pain

Pain: "an unpleasant, subjective sensory and emotional experience associated with actual or potential tissue damage." (International Association for the Study of Pain, 1979)

Pain is a distressing experience that occurs as a result of a single stimulus or series of stimuli being received and interpreted by the cerebral cortex. Pain can be considered as a protective mechanism, a warning that tissue damage has been done or is about to be done. The protective value of pain can however sometimes be impaired, as for example if degeneration occurs to the sensory nerve network responsible for conducting information to the central nervous system. Nurses in their work sometimes encounter people who, on the basis of tissue damage that has occurred, are surprisingly free from pain. More commonly though it is the experience of pain that will first alert a person to the fact that something is wrong. "Of all the symptoms that take patients to their doctors, pain is undoubtedly the commonest and the most distressing" (Smith 1985).

The physiology of pain (and its management) can best be understood by examining three distinct areas: reception, perception, and reaction.

Reception

The tissues of the body contain specialised sensory receptors and when these become stimulated, by either pressure or stretching, heat or cold, or whenever any degree of trauma to the tissues occurs these receptors convert the stimuli into nerve impulses. These impulses are then conveyed to the central nervous system, where the information is further relayed and eventually acted upon.

There are in fact two types of peripheral sensory nerve fibres that convey impulses to the central nervous system. Small-diameter myelinated (fast) fibres, which can conduct information quickly, and even smaller diameter, unmylinated, (slow) fibres. Three distinct levels of transmission exist. First, from the periphery to the posterior grey matter of the spinal cord. It is here, at this second level, that the fibres conducting pain synapse and cross to run from the anterior grey matter to the thalamus. These fibres synapse again at the thalamus and third neurone carries the information to the sensory cortex. A specialised area containing small neurones within the posterior horns of grey matter called the substantia gelatinosa acts as a kind of filtering station where the quality of the impulses reaching this area is processed. It is here that some impulses are held or checked whilst others are allowed to pass through. The "gate control theory" is an attempt to explain how this filtering mechanism operates.

Perception

The conscious awareness of pain occurs when impulses reach the cerebral cortex although it is also thought that the perception of pain also commences at sub-cortical levels, probably within the thalamus. Substance P, a peptide, is a specialised neurotransmitter, which is thought to activate the pain receptive areas in the nervous system. Smith 1985. It is also important to be aware that the body produces endorphins enkephalins and dynorphins (naturally occurring opioid 'pain killers') and these play a part in modifying the intensity of pain.

The degree by which pain is experienced varies from person to person and because pain is such a subjective experience it is difficult to quantify. To address this problem in clinical practice nurses now employ the use of pain score charts as one method for assessing whether adequate pain relief is being achieved.

Reaction

How a person reacts to pain will depend upon a wide variety of factors, for example the intensity of the perception, whether the pain is of acute or chronic nature, how old the person is (young people tend to express pain openly whilst older people tend to be more stoical), and previous experiences of painful incidents and how these were resolved. Responses to pain involve stimulation of voluntary muscles. This can be observed in the face of someone who is in pain and also by the immediate reactions that we all make when for example we stub our toe or inadvertently touch a hot surface. At the same time we may cry out or use some other kind of uncharacteristic expression! The autonomic nervous system also comes into play when pain is experienced. Sympathetic arousal is produced by low-intensity pain e.g. heart rate speeds up, blood pressure rises, whilst in severe pain parasympathetic stimulation is more likely to occur - the heart rate slows and blood pressure falls.

References

For a more complete overview of pain, see our Open Learning on the topic.

I have had a headache for 3 days and nights worse when I cough or sneeze or when I get up. Do you think I should see the doctor? My periods started 2 days ago.

27th March 2000

It would be wise to consult your doctor considering that your headache has lasted for several days. Headaches associated with the menstrual cycle tend to ease when the period begins - in your case the headache has continued. Your description hints at an infection of a paranasal air sinus, but as you will be aware there are many potential causes of headaches. Your doctor will probably ask you to describe the pain, for example whether it is dull or sharp, where it seems to be located, the times of day that you experience it, and which activities seem to make it worse. With a careful health assessment it should be possible to determine the cause of the headache and find a way to relieve it.

After cooking with hot chillies, my finger tips burned for a long period of time (and still are as I type this), presumably because of the chemical "Capsaicin," which I read about in one of your articles. How can I relieve this burning in my fingertips? I have washed my hands many times since I was cooking, and even tried soaking my fingertips in milk. But those didn't work. Any suggestions?

26th March 2000

Various substances have been found to moderate the burning sensation produced by capsaicin, but they are not the sorts of thing found in an average household. For example, an extract from the stem of the orchid Epidendrum Mosenii (Ferreira et al, 2000), the anaesthetics lidocaine (Koppert et al, 2000) and EMLA (Yosipovitch et al, 1999), and a cannabinoid (Ko and Woods, 1999). One of the reasons behind this research is to find a way of reducing the unpleasant burning sensation produced when capsaicin is applied to the skin in the treatment of the chronic neurogenic pain that follows shingles. Using capsaicin alone, the discomfort of the treatment during the first week causes many patients to give up prematurely.

If the idea of applying a local anaesthetic to your finger tips before cooking with chillies is not appealing, the other options that you have are prevention: manipulate the chillies with a fork while cutting to avoid contact with the skin or wear disposable gloves, or adaptation: use the chillies so regularly that you become tolerant of the effect.

References

Further Information about Capsaicin

Having smashed both left & right calcanii (heel bones), under gone surgery 3 times. Last operation sub-talar fusion. Constant pain. Tried DHC 120mg, Co-Codamol 30/500, Voltarol 75mg, Amitriptyline 50mg etc. GP wants me to try morphine but I have refused as I am only 31 years old. Please help.

2nd April 2000

Your GP will have taken into account a range of options and discussed these with you before suggesting an opiate analgesic such as morphine. If referral to either an acute or chronic pain management clinic has not yet been tried it will be worth discussing this with your doctor. Pain control clinics are gradually becoming more widely known and tend to be located within acute general hospitals. It is possible that they may initiate other methods of relief in collaboration with your GP. In addition it will be worth seeking advice from a complementary health care practitioner.
Although there have been studies of heel pain and different ways of treating it, a recent review came to the conclusion that the scientific evidence so far is not good enough to determine which treatments are effective (Atkins et al, 1999).

Reference

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